Immune System Inspired Strategies for Distributed Systems

Modular RADAR: Immune System Inspired Strategies for Distributed

Systems

Soumya Banerjee and Melanie Moses

Distributed Systems• Distributed sensors– Environmental monitoring– Disaster relief– Military operations

• Multi-robot control• Wireless sensor networks• Intrusion detection systems• Peer-to-peer systems

Properties of Distributed Systems

• Physical space is important• Resource constrained (power, bandwidth)• Performance scalability is a desirable feature

Natural Immune System

• Operates under constraints of physical space• Resource constrained (metabolic input,

number of immune system cells)• Performance scalability is an important

concern (mice to horses)(Banerjee and Moses, 2010, in review)

Problems Faced by the Immune System (IS)

• Only a few IS cells can respond to a pathogen

Search Problem

• They have to search throughout the whole body to locate small quantities of pathogens

Response Problem

• Have to respond by producing antibodies

Nearly Scale-Invariant Search and Response

• How does the immune system search and respond in almost the same time irrespective of the size of the search space?

Crivellato et al. 2004

Solution?

Lymph Nodes (LN)

• A place in which IS cells and the pathogen can encounter each other in a small volume

• Form a decentralized detection network

Decentralized Detection Network

www.lymphadvice.com

Modular RADAR

• Search is now– modular– efficient– parallel

We call this a modular RADAR (Robust Adaptive Decentralized search Automated Response)

Lymph Node Dynamics

Lymph Node Dynamics

Lymph Node Dynamics

Scaling of LN Size and Number

• this is in qualitative agreement with data• need more data

€

T = tlocal + tglobal

T = tdetectDC + tmigrate

DC + tdetectDC ,cTcell + tcomm

After minimizing we have

N ∝M 4 / 7,where N is the number of LNs

VLN ∝M3 / 7,where VLN is the size of a LN

Banerjee and Moses 2010

Summary

• There are increasing costs to global communication as organisms grow bigger

• Semi-modular architecture balances the opposing goals of detecting pathogen (local communication) and recruiting IS cells (global communication)

• Can we emulate this modular RADAR strategy in distributed systems?

Peer-to-Peer Systems

• Used to provide distributed services like search, content integration and administration

• Computer nodes store data or service • No single node has complete global

information • Decentralized search using local information

to locate data

Semantic Small World (SSW) P2P Overlay Network

• Represents objects by a collection of attribute values derived from object content

• Aggregates data objects with similar semantics close to each other in clusters in order to facilitate efficient search

• It maintains short and long-distance connections between clusters.

• The long-distance connections follow a precise probability distribution making the whole overlay network small-world (Kleinberg 2000)

* M. Li et al. 2004

Semantic Small World (SSW) P2P Overlay Network

adapted from M. Li et al. 2004

Bounds for Efficient Decentralized Search in SSW

• Average search path length for search across clusters is

where n is the total number of nodes, c is the number of nodes in a cluster,

l is the number of long-distance connections per node

€

tglobal =Olog2(n /c)

l

⎛

⎝ ⎜

⎞

⎠ ⎟

M. Li et al. 2004

SSW with Modular RADAR

• Our contribution is to – vary the cluster size– vary the number of long-distance connections

as

– such densification is seen as an emergent property of technological networks (Kleinberg 2004) and also incorporates redundant paths€

l = log(n /c) = log(numclusters)

tglobal =O(log(n /c))

Time to Search in SSW with Modular RADAR

minimizing by differentiating with respect to c we have

€

T = tlocal + tglobal

T =α 1c1/ 2 +α 2 log(n /c)

€

c =O(log2 n)

T =O(logn − loglogn)

Other Application Areas

• Similar tradeoffs could exist in– Intrusion Detection Systems– Multi-Robot Control– Wireless Sensor Networks

Summary• The immune system (IS) and distributed

systems operate under similar constraints• The IS has evolved a sub-modular RADAR

architecture to arbitrate between local and global communication between distributed detectors

• Similar tradeoffs also exist in distributed systems

• Such a modular RADAR approach is shown to improve search times and robustness in a P2P system

• Can be applied in other distributed systems

Acknowledgements

• Dr. Melanie Moses• Dr. Alan Perelson• Dr. Stephanie

Forrest• Dr. Jedidiah Crandall• Dr. Rob Miller• Dr. Sam Loker

• SFI Complex Systems Summer School

• Travel grants from PIBBS (Dept. of Biology, UNM)

• Travel grants from RPT and SCAP (UNM)

• NIH COBRE CETI grant (RR018754)